Typewriter with magnetically retained platen



United States Patent TYPEWRITER WITH MAGNETICALLY RETAINED PLATEN Eugene A. Smitherman, Shreveport, La.

Application February 11, 1955, Serial No. 487,630

6 Claims' (Cl. 197-145) This invention relates to mounting and driving connections for typewriter platens, and more particularly relates to a typewriter platen floatingly mounted in the carriage by a magnetic retention means.

It is an object of this invention to provide an improved mounting construction with a magnetic retention mounting on the carriage which will control the typewriter platen and will facilitate its removal so as to allow the use thereon of paper longer than the platen or the carriage.

It is another object of this invention to construct a platen which may be extended by simple additions thereto so as to support the paper during the typing operation at and beyond one or both sides of the carriage.

Still another object of this invention is to provide a driving means to rotate the platen during the typing operation, said driving means being so mounted with respect to the ends of the platen as not to interfere with the paper mounted on the platen should it project beyond the sides of the carriage.

Referring to the accompanying drawings, wherein is shown a preferred embodiment of the invention, but not the only form contemplated:

Figure 1 is a side elevation of the platen and its mounting on the carriage;

Fig. 2 is a longitudinal section of the platen on line 2-2 of Fig. 1;

Fig. 3 is a cross-sectional view on line 3-3 of Fig. 1 showing the platen rotating means in elevation;

Fig. 4 is a plan view of the line spacer; and

Fig. 5 is a part side view and part axial section of the platen with extensions attached thereto at each end, drawn to a smaller scale.

In the drawings like parts are indicated by the same characters of reference throughout the several views.

In the embodiment of the invention shown in the drawings, which comprises a typewriter provided with the usual carriage, the platen is supported on parallel rollers 11, which run lengthwise of the carriage 12 and are rotatably mounted thereon. These rollers are actuated to advance the platen line by line by spacer mechanism having a ratchet wheel 13 having an axle 14, rotatably mounted on the brackets 15-15, extending upwards from the carriage at one side of the writing position. This pivot axle may advantageously be extended and have a knob (not shown) placed thereon which will enable the manual rotation of the rollers 11 and thereby the platen 10, and thus correspond in operation to the knobs now customarily placed on each end of the platen. The brackets 1515 are rigidly mounted on the base of the carriage 12 and support the journals for the rollers 11 at their adjacent ends. A gear wheel 16 is mounted on the pivot axle 14 to rotate with the ratchet 13, and two idler gears 17, 17 are mounted on the bracket 15 in engagement with the gear wheel 16, to be driven thereby when the ratchet 13 is turned. The adjacent ends of the rollers 11 are fitted with gears 18 engaged by the gears 16, 17, respectively, which serve to drive these rollers in the same direction and at the same rate of speed.

The ratchet operating mechanism comprises the finger crank lever 19, shown in Fig. 4, pivoted on a bracket 20, and having its inner arm connected through the linkage 21, so as to oscillate the ratchet catch 22 back and forth as shown in Figs. 3 and 4. This moves the ratchet wheel 13 through one or more spaces according to the setting of the spacing mechanism as is well understood. The finger crank and ratchet drive mechanism referred to above, rotates the rollers 11 equally and in the same direction, which causes the platen 10 to rotate a corresponding distance as is clear from an examination of Fig. 3, and thus advances the paper held thereon one or more lines as is desired.

The platen covering 23, shown in Fig. 2, which holds the paper by frictional contact between itself and the rollers 11 on which it rests, may be of soft rubber, plastic or other material possessing a high frictional coefficient as to the paper. This covering is mounted on a non-magnetic tube 24, which may be of aluminum, comprising the body of the platen.

Two spring loaded paper retaining fingers 25, 25, shown in Figs. 1 and 3, are mounted on the carriage 12 in front of the platen 10 to assist in holding the platen and the paper mounted therein in desired writing position. Behind the platen is a paper retaining strip of sheet metal 26, also rigidly mounted on the carriage to support the parts of the paper or map which may lap around the platen.

At each end of the platen, shown in section in Fig. 2, is a metal block or insert 27 which blocks serve to hold the platen in place as well as to provide connecting means for the platen extension members. An axial socket 28 is formed in each of these blocks which is provided with radially movable detents 29 for engaging in the groove 30 formed in and surrounding the end of each platen extension member 31, as shown in Fig. 5.

These extensions 31 may be added to the platen 10 at either end as needed to support wide sheets and are held in place by any suitable connecting means, such as a spring loaded ball mounted in radial recesses formed in the block 27 and which engages in the groove 30, described above, or other readily operated dismountable connection or joint, as is weil known in the art of joint connections. These extensions may be as long as desired and are made of aluminum or other light nonmagnetic material. They may be rubber covered or have a roughened surface to support the paper that is rolled around the platen 10, although this is not essential. These extensions need not have a typing surface thereon as they are simply used to support the paper that overlies the end of the platen, all of the typing being done on the platen at a fixed typing point characteristic of this type of machine.

Mounted on each end of the carriage frame are two electro-magnets 32, 32, having poles 33 embracing the lower part of the adjacent platen, shown in Fig. 1. These electro-magnets are energized by means of an insulated conductor 34 wound there around as shown in cross section in Fig. 1. This conductor leads from a suitable source of electric power and has a control switch, not shown. The blocks 27 form pole pieces for the electromagnets.

While two electro-rnagnets mounted on the carriage frame cooperating with two metal inserts within the platen are used for convenience in this description, it is understood that one or more electro-magnets may be used, each magnet having at least one metal insert within the platen.

This typewriter operates in the usual manner so far as the action of the keys is concerned and has found use in typing on paper that would normally not fit within the typical typewriter carriage, such as maps, charts, etc., but obviously it can be equally well used for typing on paper of normal size.

The paper is inserted around the platen and is located in position by means of the spacer bar 19, operating through the two rollers 11, the platen being held in a floating position by means of the electro-magnets 32 against the supporting and driving rollers, the paper coming between the platen and said rollers. As the paper is fed in, it passes between the rollers and the platen, and it is supported by the rear support 26 and is held back against the platen by the fingers 25. The type, not shown, strikes the paper in the usual manner through the ribbon, also not shown. When the typing operation is completed the switch controlling the electro-magnets 32 is operated to de-energize these units. The platen may then be removed from the carriage with the paper thereon, as there is no mechanical connection between the platen and the carriage.

The magnetic force exerted by the electro-m-agnets upon the metal blocks 27 in the platen operates through the paper and neither interferes with the paper nor is interfered with by the paper, which may extend a substantial distance beyond either or both ends of the platen and the carriage without obstructing the typing operation.

The supplemental supports 31 may be attached at either or both ends of the platen for supporting the paper extending beyond the ends of the carriage and may be somewhat flexible as they are not intended to be typed upon and therefore do not need to be rigid so long as they keep the paper from getting out of alinement and crinkling.

While in the above description two electro-magnets are specified, one at each end of the carriage, it is to be understood that one or more than two magnets may be employed cooperating with a magnetic metal within the platen. This metal may be divided into pieces so that each cooperates with an individual magnet or one piece of metal may be used with a plurality of magnets.

It is contemplated that various modifications of the invention may be made to suit special conditions, and the invention is not restricted to the embodiment shown and described.

on each end thereof, a free floating platen resting on said carriage, a magnetic metal insert in each end of the platen centering with said magnet to releasably hold the platen positioned with respect to the carriage, each end of said platen having'a female joint connection for engagement with an extension means having a corresponding male joint connection and locking means associated with said joint connections.

3. A typewriter carriage having a magnet mounted at each end thereof, a free floating platen resting on said carriage, a magnetic metal polepiece in each end of said platen centering with said magnet to releasably hold the platen positioned with respect to the carriage.

4. A typewriter carriage having a cradle and at least one magnet thereon, a free floating platen resting on said carriage, said platen containing a magnetic metal insert opposite each magnet cooperating therewith to releasably hold the platen positioned with respect to the carriage, said platen being reversible end for end in the cradle, and means wholly independent of said platen associated with the cradle for rotating said platen step by step, said platen comprising joint means at least at one end thereof. for engaging with an extension piece provided with joint means adapted to cooperate with said platen joint means for extending the axial length of said platen.

5. A typewriter carriage comprising a cradle, a freefloating platen resting on said cradle and at least one pair of mutually attractive magnetic elements, one of said pair of magnetic elements being carried on said carriage and the other of said pair of magnetic elements being carried in said platen.

6. A typewriter carriage comprising a cradle, a freefloating platen resting on said cradle and at least one pair of mutually attractive magnetic elements, one of said pair of magnetic elements being carried on said carriage and the other of said pair of magnetic elements being carried in said platen, said cradle including a plurality of friction rollers having axes parallel to the axis of said platen supporting said platen, and means for effecting step by step rotation of at least one of said rollers.

References Cited in the file of this patent UNITED STATES PATENTS 833,635 Rogers Oct. 16, 1906 855,011 Lear May 28, 1907 1,186,268 Barnaby June 6, 1916 1,281,102 Tucker et a1. Oct. 8, 1918 1,283,367 Tucker Oct. 29, 1918 1,336,928 Simmons Apr. 13, 1920 2,706,762 Alexander et a1 Apr. 19, 1955 

